1. Field of the Invention
The present invention relates to a solid-state image pickup device having a plurality of color filters corresponding to a plurality of pixels, a method of manufacturing the same and a camera having this solid-state image pickup device.
2. Description of the Related Art
FIG. 1 is a plan view of an entire CCD solid-state image pickup device of an interline transfer type. A chip 11 of this CCD solid-state image pickup device has an image pickup region 12 formed by arraying a plurality of pixels. FIG. 2 schematically shows a camera using the chip 11. In this camera, the image of light from a target object is formed in the image pickup region 12 of the chip 11 through an optical system 14 including a lens 13. The chip 11 of the CCD solid-state image pickup device is driven by a driving system 15 including a timing generator. The output signal from the chip 11 is converted into an image signal through various signal processing operations in a signal processing system 16. FIG. 3 is an enlarged view of a portion of the camera near the chip 11 and the optical system 14.
FIGS. 4A to 5B show a CCD solid-state image pickup device having an on-chip color filter for a complementary color system according to the first related art of the present invention.
FIGS. 4A and 5A show a central portion 12a of the image pickup region 12. FIGS. 4B and 5B show a peripheral portion 12b of the image pickup region 12. In this first related art, a p-type well 22 is formed in an Si substrate 21. A p-type region 23 as a hole accumulated region and an n-type region 24 closer to the surface of the Si substrate 21 than the p-type well 22 constitute a sensor 25.
A p-type region 26 adjacent to the sensor 25 serves as a read out portion, and an n-type region 27 adjacent to the p-type region 26 serves as a vertical transfer portion. A p-type well 31 is formed under the n-type region 27. A p-type region 32 adjacent to the n-type region 27 serves as a pixel separation portion. An SiO.sub.2 film 33 as a gate insulating film is formed on the surface of the Si substrate 21. A polysilicon film 34 on the Si substrate 21 forms a transfer electrode.
The polysilicon film 34 is covered with an SiO.sub.2 film 35 or the like as an insulating film. The Si substrate 21 and the SiO.sub.2 film 35 are covered with an SiO.sub.2 film 36 as a passivation film. A light-shielding film 37 consisting of an Al film, a W film or the like is formed on the SiO.sub.2 film 36. An opening 37a corresponding to the sensor 25 is formed in the light-shielding film 37.
The light-shielding film 37 and so on are covered with an SiN or SiO film 41 as a passivation film. A planarizing film 42 is formed on the SiN or SiO film 41. A red filter 43a, a blue filter 43b and a yellow filter 43c on the planarizing film 42 are patterned into a checkerboard pattern corresponding to pixels, which constitute an on-chip color filter 43.
The on-chip color filter 43 of this first related art is used for a complementary system, so the blue filter 43b and the yellow filter 43c are stacked to form a green filter, as shown in FIGS. 4A and 4B. A planarizing film 44 and an on-chip lens 45 are sequentially formed on the on-chip color filter 43.
FIGS. 6A and 6B show a CCD solid-state image pickup device having an on-chip color filter for a primary color system according to the second related art of the present invention. The second related art substantially has the same arrangement as that of the first related art shown in FIGS. 4A to 5B except that the on-chip color filter 43 has a single-layer structure.
When the exit pupil of the lens 13 of the camera shown in FIGS. 2 and 3 is close to the chip 11, light 46 is incident on the on-chip lens 45 at the central portion 12a of the image pickup region 12 almost in parallel to the optical axis of the on-chip lens 45, as shown in FIGS. 4A and 6A. At the peripheral portion 12b of the image pickup region 12, however, the light 46 is incident on the on-chip lens 45 obliquely with respect to the optical axis of the on-chip lens 45, as shown in FIGS. 4B and 6B.
For this reason, in the first and second related arts, the optical axis of the on-chip lens 45 is made to match the center of the opening 37a of the light-shielding film 37 at the central portion 12a of the image pickup region 12, as shown in FIG. 5A, although the displacement amount between the optical axis of the on-chip lens 45 and the center of the opening 37a of the light-shielding film 37 is increased toward the peripheral portion 12b, as shown in FIG. 5B.
As is apparent from FIGS. 4B and 6B, the ratio of the light 46 which is focused by the on-chip lens 45 and made incident on the sensor 25 of each pixel is high even at the peripheral portion 12b. Therefore, shading due to the incident angle of the light 46, i.e., a phenomenon that the sensitivity gradually changes from the central portion to the peripheral portion on the image pickup output screen is suppressed.
Recently, the displacement amount between the on-chip lens 45 and the opening 37a at the peripheral portion 12b is increasing along with a reduction of the effective size of an optical system. When the exit pupil distance of a lens is 3 mm, the incident angle of the light 46 is about 50.degree. and the displacement amount of the on-chip lens 45 almost reaches 1/2 the pixel pitch.
However, in the first and second related arts, the center of the on-chip color filter 43 of each pixel matches the center of the opening 37a even at the peripheral portion 12b, as shown in FIGS. 4B and 6B.
As is apparent from FIGS. 4B and 6B, the light 46 incident on the sensor 25 of each pixel passes through the on-chip color filter 43 of an adjacent pixel, resulting in a mixed color, or the light 46 passes through only part of the thickness of the on-chip color filter 43 of the pixel, resulting in a deviation of the spectral characteristics from desired characteristics. For this reason, in the first and second related arts, a high-quality image having no color irregularity can hardly be obtained.
To prevent color irregularity, displacement of the on-chip color filter 43 of each pixel from the opening 37a has also been examined. In this case, however, only the distance from the central portion 12a of the image pickup region 12 to the opening 37a of each pixel is taken into consideration, and the thickness of the on-chip color filter 43 or the height from the surface of the Si substrate 21 is not taken into consideration. For this reason, it is still difficult to obtain a high-quality image having no color irregularity.